CA1084468A

CA1084468A - Pulverising apparatus with a toothed disc

Info

Publication number: CA1084468A
Application number: CA244,402A
Authority: CA
Inventors: Wilhelm Eirich; Gustav Eirich
Original assignee: Individual
Current assignee: Individual
Priority date: 1975-01-29
Filing date: 1976-01-28
Publication date: 1980-08-26
Also published as: ATA7376A; US4050637A; JPS592538B2; DK137916C; ZA76406B; CH611535A5; SE419176B; BR7600526A; AT351910B; DK137916B; DE2503621C3; IN142648B; FR2299086B1; DE2503621B2; BE837873A; GB1506968A; IT1056587B; ES444577A1; DK35376A; JPS51100377A

Abstract

Abstract of the Disclosure A pulverizing apparatus is particularly suited for pulverizing elastic, viscous and bulky materials as well as refuse and other waste mate-rials. The apparatus includes a driven container and at least one high-speed tool eccentrically disposed within the container and having a shaft substan-tially parallel to the axis of the container. The tool has at least one toothed disc in a plane transverse to the tool shaft. The disc dips into the material present at the container wall. The tool is displaceable generally radially within the container.

Description

~ ~08446B
The invention relates to a pulverising apparatus, particularly $or elastic, viscou6 and bulky materials, as well as refuse and other - waste materials, with a driven container and at least one eccentrically disposed high-speed tool which has a shaft disposed approximately parallel with the axis of the container.

It is known that environmental experts are increasingly aware~
with the growing quantities of refuse at both municipal and parish level, as well as from industry. Large and modern refuse elimination ~ plants, by virtue of circumstances, can only convert waste into I another form even though the latter may occupy less volume than the starting material.

Also the situation in the case of stocks of raw materials in world economy have resulted in the knowledge that it is essential t to strive for better utilisation of available raw materials, manufac-i turing resldues and waste. Desirable, therefore, ~Jould be an apparatus for comminuting heterogeneous materials, e.g. household and industrial refuse, occurring in large quantities, even when supplied in sack6, and of the high grade materials contained in this refuse, such as paper or packaging materials of all kinds, textiles materials, etc.
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After their comminution, such materials could be fe to other furtherprocessing stages, but a necessary condition is a suitable pulverising apparatus.

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A further problem exists in the paper and woodfibre board producing industry: timber production is incapable of coping with the rapidly increasing consumption of paper. Therefore, it seems important to be able to process tree residues such as branch and root timber and also bark, hitherto unused, in the aforesaid industry for - - 2 ~

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1~)84468 the production of papers, fibreboard and insulating board.
:, . .
- ~ - Known methods are scarcely capable of processing elastic, viscous, . ..... . . . .
-~ moist, sticky or bulky materials. At le~s~, no efficient and competi-tively priced machine is available for a rational pulverising of such materials.

.
~ he incineration plants often used have the great disadvantage of leaving about 35 to 50~ by weight of residue, even though the - volume shrinks to about 1 h 0th that of the starting material.

, The depositing of these residues without adversely affecting the nature of the ground-water is a difficult problem. Also contamination of the air by combustion gases creates difficulties. Only very expensive purification plants can either purify the waste gases and carry away the poison in liquid form, jeopardising the ground-water, and also this is frequently undesirable.

Furthermore, it must be remembered that for example refuse contains large quantities of metal and in any rational pulverising of such mass materials, it is particularly essential to heed a high rate of throughput of the pulverising machines, with economical power consumption and a low rate of wear. Separation of the metal parts, at least of the ferrous metals, presents difficulty particularly when these parts are supplied to the pulverising machine in filled refuse sacks, cartons or bundles. The over-belt magnets and other magnetic separating devices which have been used in the past are scarcely capable of separating iron parts which are present in refuse bags, sacks, cartons and the like.

q`herefore, the invention is based on the problem of providing a pulverisine apparatus of the type mentioned at the outset, which can ~084468 very effectively and with minimum mechanical-technical complication provide for both manufacturing residues and also refuse or raw materials of practical-ly any range of consistency, to be pre-comminuted or finely comminuted and blended, providing if necessary also a magnetic separation phase.
According to the invention, there is provided a pulverising appara-tus comprising a rotatably driven container and at least one eccentrically disposed rotatably driven high-speed tool having a shaft disposed approximate-ly parallel with the axis of the container, characterised in that the high-speed tool is provided with at least one toothed disc, the plane of which is transverse to the tool shaft and which partially dips into material to be pulverised which is present at the container wall, and in that the high-speed tool is generally radially displaceable in the container.
The principle underlying the invention is based on the knowledge that the materials in question could be comminuted with a toothed circular disc, it goes without saying that circular saws are already known ~ se for wood and even for metal. The problem arising with the comminution of bulky, elastic and viscous materials to the point of the same being pulverised, resides in bringing the aforesaid materials into the range of action of the toothed circular disc. In this respect, use is made of the action of centri-fugal force in a rapidly rotating container which is driven at above-critical speed. In another connection and with other kinds of machines, the use of a container driven at an above-critical speed is already known. The term critical speed is understood, with regard to the container drive, to be that number of revolutions per minute at which the centrifugal force is greater than the weight of the relevant material, so that the material is pressed against the inside walls of the container.
The action of centrifugal force is advantageously aimed in two directions:

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:- - 1084468 ~ 1. The to a certain extent bulky materials which are to be finely - comminuted are, without further preliminary treatment, first ~ -introduced into the container of the pulverising apparatus and are automatically pressed agninst the inside wall of the container by the high rate of revolution (at first, the materials in question here are those which require no magnetic separation or preliminary comminution). As a result, these materials are held fast against - the rotating container wall and, at the peripheral speed of the container, they are fed into the high speed tool which rotates ' ' ~ , , -about its own axis but which is otherwise stationary. In this way, engagement is reliable and high comminuting efficiency is trans-mitted, because the speed of revolution of the container is relatively high.
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- 2. With effect from a certain degree of fineness of the comminuted , material, further comminution takes place and finally, fine grinding is only rational and effective if sufficiently powerful pulses can be transmitted to the material to be com~inuted. These are shocks which load the particles beyond their breakage limit.
With increasing degree of fineness, however, the mass weight of .. . . .
the already pre-comminuted particle~ becomes increasingly smaller, so that the pulse, product of mass x velocity, likewise diminishes greatly, and consequencly the comminuting effect also diminishes.
Surprisingly, the already pre-comminuted particles of low stationary mass, are by reason of the measure according to the Invention,-namely by reason of centrifugal force, so pressed against the container wall that they cling thereto at a multiple o~ the earth's acceleration. Thus, their mass weight is artificlally increased and in turn the transmission of a high pulse for further ultra-fine comminution of the particles is guaranteed.

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` ~ 3L084468 The pulverising apparatus according to the invention is suitable for virtually all materials, particularly for the processing of the substances mentioned at the outset, both powedered and sand-like, dry as well as moist and also sticky compositions such as for example clay or clay mixed with pieces of chalk, fabrics, shoes and other viscous materials being readily pulverised. The machine according to the invention reduces by cutting, shredding, tearing, beating, squashing and by abrasion. In the case of a material such refuse which is composed of basically different materials, this versatile functioning with a very simple and effec~ive apparatus is of deci- -sive significance. Proportions of hard material in the waste, such as for example glass, china, etc., are required to be reduced to the granular size of fine sand, while it is sufficient for rottable materials to be reduced to 10 mm and downwards. The container mentioned at the outset may be smooth walled or may also be produced from perforated or ribbed plate. It is neces-sary only to avoid relatively large raised portions on the wall surface.
In other words, pulverisation occurs in that the container may be driven at over-critical speed, the direction of rotation of the high speed tool being opposite to that of the adjacently disposed container wall so that the makerial present in the more or less large gap between the container wall and the periphery of the toothed disc is thrown out and not into this gap, which might damage the machine.
It is furthermore advantageous for a plurality of toothed discs to be mounted on the shaft one above another and at a distance from one another so that the material pressed against the container wall remains like a roll at the height of the intermediate space. It is always desirable to maintain a considerable difference in speeds between the material held and pressed against the container wall and the tool engaging this material, i.e. the circular toothed disc, in order to transmit the highest and most intensive pulses possible to the material which is to be pulverised. The aforementioned measure of mounting a plurality of toothed discs on the shaft at a distance ~ ?!

10844~8 one from another is logical particularly if, according to the invention, the shaft of the high speed tool is displaceable in an axial direction. In this case, in a first position, as many zones of goods on the container wall can be covered in annular strips as there are toothed discs mounted on the shaft. ~ -In continuous operation, the shaft is moved axially by a certain length in a slow rhythm and the desired high difference in speeds between tool and material is ensured when the material remains in a roll along that annular strip which is not so covered. The axial upwards and downwards movement of the tool shaft occurs uninterruptedly, so that the entire inside wall of the container is completely covered by the toothed discs.
Furthermore, it is expedient for a plurality of high speed tools to be disposed eccentrically in the container. Then the comminution of bulky waste materials such as packaging material, plastics containers, pieces of rubber, shoes, tubes, papers and cartons of all types, bundled and loose, will be completed particularly quickly in the machine. The pulverising apparatus according to the invention works perfectly in any range of consis-tency. In the case of fine grinding, i.e. at that condition of operation where the container is driven at above-critical speed, it is certainly essential that the direc~ion of rotation of the .. . : . . ................... : .
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~ iO84468 toothed disc be opposite to that of the adjacent container wall, as ; already mentioned at the outset. - -, - .-Otherwise, the material will cling between the tool and thecontainer, or become clogged and the tool shaft will be overloaded.

According to a further embodiment of the invention, for the purpose of pre-comminution, the container is driven at below-critical .
speed, i.e. the number of revolutions per minute at which the container is driven is so small that the weight of the material is greater than , the centrifugal force which seek6 to press the material against the inside wall of the container. The below-critical speed is used either in a separate machine which, for the purpose of pre-comminution, is disposed alongside the fine pulverising machine, or the speeds are changed in one and the same machine. In any case, where pre-com~inution i8 concerned, during which the materials still have a relatively large mass, it is possible to achieve a breaking-open of the parts, a kind . .
of coarse sawing and, for example in the case of household refuse, certainly a tearing open of bags~ cartons and sacks. Even if outwardly dried refuse sludge is being treated, lumps are destroyed and broken down so that, in principle, homogenisation occurs to a certain degree.
All this occurs under conditions of economic energy consumption and preferably a plate with a relatively broad or high container wall is used which, according to a further feature of the invention, is tilted, i.e. inclined more or less steeply, with res~ect to the horizontal.

Such inclined plates are kno~m in granulation technology. ht approximately half the height of the rising half of the plate, there -is a rapidly moving tool having at least one toothed disc and in the case of larger installations, it is possible also to use a plurality , _g_ : . . ., - , , . . -, -: . : ~ .

:. ' ' .. , , , ~ ~ , , of these tools. These rotate at moderate speed in the opposite direction to that of the container. Bundled paper which was hitherto left on the heaps of debris from incineration plants, frequently in just an outwardly charred condition, is reliably torn apart so that the material, particularly bundled and compressed materials, are accessible to the combustion air at all points.
Furthermore, it is preferred that at least one magnet is rigidly mounted on the container with the active side of the magnet facing the interi-or of the container and disposed in the regularly curved face of the container wall, and that a discharge chute is provided in the container. These measures apply to magnetic separation. At the commencement of the pre-comminution, when, while the container is inclined, the shafts of the high speed tools with the toothed washers are disposed at a greater distance from the container wall, even large-bulk materials can be fed into the apparatus. After separa-tion of the iron materials and continued comminution, the distance between the toothed discs and the container wall is diminished by the aforementioned pivoting, towards the container wall, possible to the extent of fine decom-position.
Where a plurality of toothed disc tools are disposed one after another in a container, as is the question with larger machine units, the distance from each toothed disc tool to the wall of the container is so regu-lated that the driving motors of the individual toothed disc tools operate with the same loading. This means that in the vicinity of the material intake, the toothed disc tools are at a greater distance from the container wall than those which follow.
The fitment of at least one magnet on the container - naturally, in the region of the magnet, via a magnetically insulating material B

,,"84468 such as for ex~mple V2A steel - overcomes the difficulties which have hitherto been encountered in magnetic separation. The known over-belt magnets are namely either disposed (for magnetic separation) very closely over the material which is for example passing through on a belt, so that larger pieces such as large cans, bottles, buckets, cartons, etc., cannot pass through and strike the o~er-belt magnet or, on the other hand, their distance from the material to be processed i8 50 great that the magnetic force is not sufficient for separation.
In any case, disturbances in operation occur and such disturbances do not any longer arise with the apparatus according to the invention.
In fact, by reason of the measure according to the invention, it is advantageously ensured that the material to be processed positi~ely passes through a large number-of ma~netic fields which may be disposed ~in close sequence, in the shortest of time, during co-rotation with the rotating container, the material being simultaneously subject to lively movement. Beginning with a slight circulation, this movemeht can be pursued to the point of breaking down large lumps, of viscous and hard agglomerates in the most widely diverse degrees of fineness, the materials fed in ~eing at the same time mixed, the horoughness of magnetic separation achieving optimum levels even in the case of ~ -short treatment times. Also, a throughput of large quantities is guaranteed.

According to a further development of the invention, two or more preferably four, magnets which can be switched off are disposed on the periphery and/or are evenly distributed over the height of the con~ainer wall. Preferred are electromagnets which have given the . .: . , . ~ . , . : .
best results in tests. The effect of these electromagnets i8 ~.

particularly strong if two coils are disposed one closely after the .

-- 10 _ . ~ ' ' ''- ~ :
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.:
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.: ' . : : ~, -- ' : :': ' ~ 1084468 -~ other in the direction of rotation of the container, in each case with an iron core and with a yoke in the form of an iron plate or .
the like connecting the two serially disposed cores. Then also the magnetic fields extend from one pole to the opposing pole, more or less in the direction of rotation of the container, and the force of attraction for ferrous metals in the material which is to be treated is very great. Ideally, then, the toothed disc tools, viewed in the direction of the container wall, are disposed between two double magnets 80 that tho6e iron parts which are trapped by the magnets during rotation do not or do not often enter the working range of the toothed disc tool. Also, a larger area is overed by using the double magnets described.

In the case of a special embodiment, while retaining the smooth inner face of the container wall, it is possible to use a plurality of electromagnets which are moved to the height of the container wall and which are also disposed at a distance around the periphery of the container vall, so that virtually the entire wall of the contairer is, during rotation at below-critical speed, covered by at least one magnetic field. If the container runs for example at 25 revolutions per minute, then the basic period of dwell of the material in the container is only 30 seconds and, with four magnets disposed cross-wise, the material to be treated passes through 50 magnetic fields in this time. In the upper zonF of the inclined rotating container, the non-magnetic material drops downwards, whereas the iron parts picked up by the magnets are carriçd on and are conducted to a definite place on the descending side of the half plate. There, they are either held back by a wall scraper so that the magnetic plate slides past, whereupon the ferrous metals drop into the said delivery chute dlsposed underneath, or the magnet is switched off briefly at the -- 11 -- . ~

~0~4468 discharge point so that the wall scrapers are then unnecessary. The iron parts drop into the discharge apparatus during the period of switch-off, so that the separated metals can be carried away by reason of the inclined position, by a conveyor belt, by a vibrator or the like.
A pre-pulveriser and iron separator according to the invention is completely unaffected by coarse parts and cannot clog even if unevenly loaded, even if course-lump material enters the machine, because the inside wall of the container is smooth, the aperture is exposed and discharge can take place without hindrance.
The machine according to the invention also makes it possible to -conduct finely ground material through a multiplicity of strong magnetic fields in the moving stage, in rapid sequence and for an exactly adjustable time. It is particularly convenient to use the machine according to the invention for magnetic separation from materials which are sensitive to iron contamination, such as for example raw materials in the fine ceramics industry.
Reliable separation of even fine steel particles provides considerable advan-tages because, for example in the fine ceramics industry, it is possible then to use steel grinders, particularly since the iron impurities caused by abra-sion can be removed again by the machine according to the invention. Also in the chemicals and in other branches of industry, similar advantageous pos-sibilities of application arise.
For clean magnetic separation of even fine iron particles, it is expedient to provide over the discharge chute and next to the inside wall of the container a scraping device, e.g. a wall scraper and/or round brooms.
These can then provide for a clean elimination of the iron parts separated, so that high grade cleansing is guaranteed in a very economical fashion.
Furthermore, by reason of the measure of the invention, it becomes possible to provide alongside the discharge chute a fan and blow-out orifices to pro-duce an air stream which will pass over the discharge zone, and also an opportunity of so conducting the stream of air that paper and plastics shreds, B

--- 1084~68 . ..
etc., which may be clinging to the iron parts are blown to one side as the material drops~when the magnets are switched off, so that these shreds do not penetrate between the separated iron parts.
It is advantageous furthermore to provide in the bottom of the container a discharge orifice which can be closed by a cover. For example, after 1 m long billets of young spruce, with branches and twigs and bark, have been reduced to fibres of about 1 to 5 mm, it is possible in ~r se known manner to lower a deflecting apparatus from the upper aperture in the container down to the bottom and which, within an extremely short time, will discharge all the comminuted material when the discharge orifice is open.
The apparatus is then ready for the next batch, once the discharge orifice has been closed.
It is also advantageous to provide on the shaft a separate motor for the continuous operation of the cover and for this preferably to be driven at a speed in advance of the container bottom. In this respectJ continuous withdrawal is possible even without vacuum extraction of the fine material upwards, a system which will be described hereinafter. When the empty machine is started up, the orifice contained in the middle of the container bottom is closed by the aforesaid cover being fitted. As soon as : .~
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a quantity of material sufficient for continuous operation i6 .
-present in the container, the coYer is pushed downwards in the direction of the axi~ of the rotating container, so that a dischar'ge gap is created between the container bottom and the cover. At this setting, a continuous stream of material surprisin~ly flows outof the machine,-the degree of fineness of the material processed being very high. Thus, inside the container there i6 an excellent Separation of coarse from fine matter. The cause of this separation possibly resides in the rapid circulation of the discharge stream generate~ by the toothed disc tools. Strong centrifugal forces act wi'thin this discharge stream, so that coarser and heavier parts at '' once move into the outer zone of the plate, where they are subjected to ~urther comminution, while the finer parts move towards the centre of the plate where they are discharged. Measured in relation to the container bottom, the cover mounted on a small geared motor or the like rotates positively at advancing speed. In this way and parti-cularly by reason of the further measure according to the invention whereby, viewed'in the direction of material discharge, the cover is disposed after a connector which is fixed on the outside of the connector bottom, while on the cover there is at least one curved ' delivery rib of little height, it is completely ensured that there will be no blockage in the delivery gap. In this way, it is possible even to discharge sticky and plastics compositions, particularly by virtue of the curved delivery rib which is preferably proYided and which conducts the material which arrives from above, reliably outwards through the gap. There are outstanding possibilities of controlling the quantity discharged, namely on theone hand by adjustment of a desired width of gap between the cover and the container bottom and on the other by the rotary speed of the cover.
Discharge downwards also reliably avolds inadequately comminuted ~0~34468 - - - .
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plastics residues being discharged. All this although the machine according to the invention operates on minimum expenditure; even in -the case of fully-automatic operation of theplant, during which the discharge orifice is fiO regulated that the material being discharged i6 of the desired fineness.

- In the case of another for~ of embodiment, for continuous operation with dry or nearly dry materials, a suction pipe, a supply ~ line and a covering are provided on the-upper container aperture.
i ~he supply line is preferably disposed in the middle of the container and extends far down, almost to the container bottom, so that the air streams are evenly and intensively charged with-material and for purposes of centrifugal separation are, if at all possible, caused to rotate. When the material to be comminuted has attained the I sufflciently small particle size, it will, after impact and comminution, by which the particles are briefly separated from the container wall, briefly remain in the space within the container.
When they are sufficiently small, their weight is so minimal that they can be extracted by the stream of air. Otherwise, they are again pressed against the container wall by centrifugal force. Thus, it is advantageously possible on the one hand to feed material through the supply line for comminution and, on the other, automatically to sort the comminuted material according to particle size and to extract it upwardly through the vacuum tube.

A further advantageous embodiment of the invention is charac-terised in that between the toothed disc or discs (11) and the bearing for the shaft carrying the toothed disc, there is a fan, the impeller of which is mounted on the shaft, its housing being mounted on the tool carrier of the V-belt drive, and the blow-out stream .

from which extends more or less at right-angles to the shait, and .
in that a throttling arrangement is pro~ided on the intake aperture i ~
~ - .:' : ' .
of the fan. Then, the blow-out stream from the fan i6 directed more or less at right-angles to the axis of the toothed dlsc tool. With the throttling device, it is possible to adapt the quantity of air to be extracted, to the particular conditions of operation obtaining.
This fan can also be operated as a grader (more or less according to the principle of the transverse flow grader), by providing in the vicinity of the intake aperture a rotating disc which generates a stream of air directed at right-angles to the axis of the toothed disc tool, so that the rising air, charged with ground material, has to traverse this transver6ely directed lighter air stream, whereby heavier parts entrained by the risin~ stream of air are deflected out~rardly by the transversely directed alr stream and then fall back ~-into the interior of the container.

A special embodiment of the invention is advantageously .
constructed in that in the outer zone, the toothed disc has a thick-ness of 2 to 12 mm, preferably 2.5 to 8 mm, and possible a diameter of 100 to 900 mm and preferably 300 to 750 mm. In the case of very large machine units, these dimensions are greater. From-the point of view of grinding efficiency, high peripheral or differential speeds are favourable, particularly in the case of material which has to be broken down finely. The more rapidly the particles are loaded beyond their breaking limit, the higher is the efficiency of the machine. As already mentioned, the diameter of the container depends upon the size of the machine. Important is the peripheral speed of the discs which, for fine comminution, is around 70 to 120 m/sec in the case of smaller machine units, although for special jobs, it may be higher. In the case of pre-comninution and coarse preparation, the peripheral speeds are between 1/4 to 1/2 of the values mentioned. The cost of power for loadings which do not result in breakage is substantially or completely lost and therefore the measures according to the invention are so contrived that the particles are loaded beyond their breaking limit. The material to be comminuted can, by reason of the appara-tus according to the invention, be subjected to extremely high loadings. In practice, the upper limit is determined by the edge life of the materials used for the tools.
It is therefore expedient for the relevant impact face of the teeth to be disposed radially or projecting with respect to the toothed disc. For high loadings or in order to increase the edge life, the impact faces may also be armoured. In the case of one embodiment of the invention, the form of the teeth on the toothed circular disc lies between the shape used for wood saw blades and that used for circular metal saw blades. In the case of another embodiment of the invention, it has been regared as convenient for the toothed disc to have a carrier disc underneath it, with radially disposed cut-outs, teeth which can be inserted in these latter and attached to the carrier disc, and a cover disc disposed on top. In this way, the teeth which are fitted securely for example by bolts, and then clamped in position via the two discs ~carrier disc and cover disc), can be exchanged individually as minor compon-ents.
According to a further suggestion, the teeth may consist of rect-angular flat plates which are preferably armoured in places. The pulverising process takes place substantially at the cutting edges and edges of the impact faces, so that surprisingly the action of the pulverising apparatus could be enhanced by these narrow toothed discs. The excellent suitability and surpris-ing technical action of the high speed rotating toothed discs according to the invention, for the pulverising of materials of basically different consistency, is based on the combined effect of cutting, shredding, sawing, tearing, squash-ing, abrading and comminution by shock and/or impact loading on the material B
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being treated, i.e. by hammering. The toothed disc unifies these combined working and attack effects better than any other pulverising apparatus.
Therefore, the machine is surprisingly suitable for all manner of materials, while the known machines are always designed just for definite fields, grades, jobs or quantities.
The container wall and thus the shaft of the high speed tool may be made relatively high and/or long, in order to achieve a high rate of throughput in the machine. If for example the wall height of the container is equal to the radius of the container, then the pulverising apparatus can process twice the quantity than could be processed if only a plate mill were to be used in which treatment occurs substantially only in the bottom of the plate-like container.
Many grades of material for grinding, particularly synthetic plastics, nutrients, chemicals and combustible materials are very sensitive to rises in temperature. The currently most used other grinding systems which operate continuously concentrate the loading on the relatively thin stream of material into a short time, so that the heat released cannot be dissipated rapidly enough and therefore produces very dangerous rises in tem-perature in the material being ground. In the present machine, on the other hand, a relatively large quantity of material is always present. The parti-cles picked up by the pulverising tools are immediately subject to a stream of cooling air and cooler adjacent particles. In this way, the particles are immediately cooled to the average temperature of the material present in the machine. The average temperature can easily be controlled by the quantity of air circulating in the machine, the number of toothed discs in engagement, the quantity of material being ground and possibly the use of additional cool-ants prior to charging or in the machine; yes, even the inclined position of the rotating container can have an influence.
It was mentioned above that the direction of rotation of the too*hed disc tools is generally opposite to the direction of rotation of the container.

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)84468 On the other hand, should the problem be posed of opening up material consist-ing of smaller particles, in a fibre-protective manner, then as few fibres as possible should be undesirably shortened by impact or pronounced shock effects, then synchronism of container with toothed disc at greatly differ-entiated peripheral speeds will be advisable. By this method, it is possible protectively to open up for example timber, asbestos rock, textile waste, etc., in order to obtain long fibres. By reason of the above critical rotary speed of the container during fine comminution, the material to be opened up is practically held fast by the force of centrifugal action, while the toothed disc tools provide for a cutting action.
It is furthermore advantageous for the outer free edge of the con-tainer, over its entire periphery, to consist of non-magnetic material and to provide a stationary elongated magnet in the lower zone of the inclined con-tainer. Surprisingly, this can prevent lightweight, bulky metal parts rolling off over the edge of the container before they are picked up by the magnets.
This possibility arises then if a high layer of predominantly non-magnetic material is present between the magnet and the supply of material. The non-magnetic material at the outer edge could be VA steel. The said magnet is rigidly disposed at the discharge point directly below the rotating edge of the container and is spaced at a small distance therefrom. An outwardly rolling iron body then passes positively into the field of this magnet and is trapped on the rotating wall over the length of the fixed magnet disposed underneath. During this movement, the iron body passes out of the stream of material being discharged. At the end of the magnetic field, as soon as no material is pushing its way on from behind, the iron body falls back into the container and is then in the desired mannerJ picked up by the next co-rotating magnet and is carried to the upper discharge point.
Furthermore, if the apparatus is used as a pre-pulveriserJ it is possible additionally to connect over the outer edge of the rotating container a screen edge so that the out-flowing material first passes through the screen :"
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108~1468 - ~

edge. Thus, the fine components would be separated off, while the coarser constituents flowing over it would be fed into the fine pulveriser. The material flowing out of the pre-pulveriser will in fact always contain a more or less large proportion of fine grain components which require no further comminution. It would be a waste of power to feed these fine particles to a subsequent fine pulverising machine, the container of which rotates at above -critical speed in the manner described. This measure ensures that only the coarser part is carried into the aforesaid subsequent fine pulverising appara-tus.
The screen edge may be cylindrical, circular or even polygonal. In the case of numerous materials, angular drum screens operate more favourably than cylindrical.
In comparison with the known machines for mixing or dressing sub-stances which apply in some cases similar mechanical measures as those pro-posed herein, attention is also drawn to the essential difference in that where the present apparatus is concerned, apart from the high speed tool, as a rule no other fitments are provided in the container, particularly no deflec-tors which would consume power. The apparatus could only in the case of special constructions be equipped with retractable and extending deflecting arrangements, e.g. for discharging through an orifice disposed in the centre of the bottom, or in the case of a container rotating at slow, even though~
also at over-critical speed. Preferably, thoughts are directed at the very simple embodiment with container and only one high speed tool, whereby advan-tageously quite considerable free space is available for feeding in even bulky materials. Apart from very hard abrasive substances which are usually not even reduced in size by metal saws, all materials, even ceramic substances, which occur in refuse, can be fed into the machine.
A surprising advantage of the apparatus according to the invention is the attainable increase in quality of numerous products obtained from a plurality of basic materials, e.g. optimum utilisation of natural products, ~ -~

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1~8446~

particularly those which do not multiply. For the first time by reason of the apparatus according to the invention, it is possible to exploit the knowledge that chemical reactions, particularly between solids with and with-out a proportion of liquid, the best results are obtained if the particles of the starting substances are jointly ground to the highest degree of fineness possible. In consequence, there is a merging of very fine particles which can be compared with a cold welding thereof.
The toothed discs, cutting discs, particular circular saws, have proved outstandingly suitable in the cutting and opening up of soft, medium-hard materials and even metals. The high speed rotation of the toothed disc makes it very rigid and sharp. Where the processing of liquid materials is concerned, comminution by mechanical shock transmission is further improved by the resultant cavitation, which is likewise caused by the high peripheral speeds.
Also very advantageous is the possibility of converting to granular form waste products comminuted with the machine according to the invention and blended with binders or other substances, particularly if it is desired to produce lightweight granular additives or pourable moulding compositions from mixtures of waste clay. For these, the pouring capacity is frequently decisiv~, if only one pourable material is ideally suitable for rapid and regular feeding of moulding machines. The present machine also resolves this problem in a surprisingly advantageous manner by combining the pulverising ;
process, the mixing process, combined with accurate attuning of the moisture content, and conversion of the composition into the form of a granulate.
Granulating processes can also be accelerated and intensified by simple measures, using ~he new pulverising apparatus. Upon conclusion of the pulverising and mixing process in the apparatus according to the invention, the rotary speed and angle of inclination of the container are adjusted to those ~ ;
most expedient to granulate production and the high speed tool with the toothed discs is switched over to the same direction of rotation as the container.

Ideally, the rotary speed of the toothed discs is also so attuned that there B

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. 1084468 is a~slight lead over the container by which an additional rolling movement i6 imparted to the material which is to be granulated. This is vital to the rapid performance of the granulating process.

In addition, the Jet of discharged material produced uninter-ruptedly inside the container by the toothed discs is ideally suited for heating or cooling purposes. The stream should then be exposed - to.hot or cold gases.

~ here the processing of viscous, sticky compositions is concerned, - ~ the amount of energy consumed by the toothed discs can be substantially reduced if, during the wor~.ing process, the exposed surfaces of the discs are kept wet by being sprayed with liquid or wetting agent.
This considerably reduces the friction between the disc and the material being treated and reduces the power consumption without adversely affecting the opening-up effect. In contrast to other preparation machines, the toothed discs according to the inventlon - have only a s~all part of their surface engag m g into the material being treated, so that ideal conditions are created for keeping the surfaces wet with spray jets, so increasing power utilisation.
, - Further advantages, features and possibili~es of application of the present invention will become manifest from the enusing descrip-tlon in conjunction with the drawings, in which:

Fig. 1 diagrammatically shows in plan view a pulverising apparatus according to the invention, having two eccentrically disposed high speed tools, a discharge orifice and the apparatus for - adjusting one tool in the container;
Fig. 2 is a sectional view through a special embodiment of pulverlsing apparatus according to the invention with the container axis tilted with respect to the horizontal;

-~3 , ~11184468 Fig. 3 i6 a plant view of three special embodiments of a toothed disc and Fig. 4 is a 6ide view of the high speed tool with the chucking device disposed at the top;
Fig. 5 is a side view of another embodiment of the device shown as a pre~comminuting machine with magnetic separation;
Fig. 6 is a plan view of the embodiment of machine shown in ~ig. 5;
Fi8. 7 shows a further embodiment of comminuting apparatus according to the invention, in a view similar to 'that in Fig. 2 but - with a fan disposed above the toothed'disc tool and showing ! more clearly the discharge orific'e with the rotating cover;
Fig. 8 is a broken away plan view of the right-hand upper part of the apparatus according to Fig. 7;
( Fig. 9 is a plan view ol a special embodiment of a bottom carrier ¦ disc for another type of toothed disc, and Fig.10 shows the embodiment of toothed disc provided by means of the carrier disc according to Fig. 9 and having flat rectangular plates which-are armoured in places.

The container 1 of the pulverising apparatus according to the embodiment shown in Figs. 1 to 4 can during pulverising be driven - at above-critical speed of various stages and at different speeds:
possibly for pre-comminution at a lower even though abave-critical speed, and in the case of a fine pulverising stage, at a speed which ' is increased to considerably higher levels for an increase in mass up to 2 to 100 times (in the case of fine granulation possibly 300 times).
The container wall is smooth or slightly ribbed on the inside. As indicated in Fig. 1, the alreay pre-comminuted materi~ hich has to be further reduced in s;ze is sho~m at 2 as resting thereon. The circular toothed disc 3 of the right-hand high speed tool or 3' of '.

.~ , .

~ 1084~68 the tool shown on the left inbroken lines in Fig. 1 has its periphery partly immersed in the materlal 2. The high speed tool generally designated 4 has, as shown in Fig. 4, five superposed circular toothed discs 3, 3', etc. For rapid exchange purposed, these toothed discs are separably mounted on the shaft 5 of the tool 4, the shaft having atits upper end a V-belt pulley 6 and being driven by the motor 8 via .
the V-belt 7 shown diagrammatically in Fig. 2.
, Fig. 1 shows a deflector which is only required when the machine is operating periodically, being then used for discharging the material .
through the discharge orifice 12 in the middle of the contairer. When bulky material is being processed, during the actual pulverisin~
process the deflector 14 is raised so that it does not constitute an obstruction. In the case of non-bulky material, the deflector can either be-pivoted or lifted out about an axis 15 so that it does not engage into the layer of material during the pulverising process and will not cause any friction losses. When handling bulky refuse, the largest possible ~ree inlet opening should be provided. Therefore, it is convenient in the case of the embodiment sho~m in ~ig. 2 having ., ,: . , .
the inclined conta mer, to dispose the axes of the high speed tools 4 in the upper zone of the container.

The high speed tool 4 can be raised, lowered and pivoted by the tool carrier 20. By the pivoting movement of the carrier, the distance between the toothed discs 3 and the wall of the container 1 can be maintained constant even as the toothed discs become smaller due to wear. Fbrthermore, this pivoting movement offers an opportunity, in the case of intermittent charging of the parratus, if for example relatively large quantities of material are suddenly fed, of moving the shaft of the high speed tool 4 by automatic control means and 1084~68 using hydraulic pivoting apparatus, and the toothed discs 3, at a greater dist~nce from the container wall, so that non-uniform layers of material can be passed between the container wall 1 and the toothed discs 3 without any shock loading of the drive element~. As pulveri-sation proceeds, the distance between the toothed discs and the container wall can be successivelg reduced. This increases the insensitivity of the machine to hard and lumpy foreien bodies.

Thé pivoting movement of the tool carrier 20 furthermore makes it possible to pivot the high speed tool 4 into the reeion of the aperture, not described in greater detail-, disposed at the upper edge of the container 1, so that after a few crewed connections have been undone, the tool 4, together with the toothed discs 3, 3', etc., can be withdrawn from the machine and quickly eY~changed for a second tool which has sharpened toothed discs.

Fig. 2 show6 the pivot 21 disposed outside the container 1 and carrying the tool 4 together with the driving motor 8. By periodic -raising and lowering of the pivot 21 by means of a small hydraulic ran~, it is possible for the toothed disc6 to cover the overall height of the side wall of the container. If the machine is equipped with more than one high speed tool 4, generally the raising and lowering movement of the tool shaft will be adequate. Thus, a constant shiftirg of the material being processed is achieved, so that the toothed discs of the other tools which are not vertically adjustable will constantly engage new layerfi of material.

If it is intended, in the case of periodic operation, to discharge the treated material through the container orifice 12, the container 1 is switched to a sub-critical speed during the emptying process. The toothed discs 3 then clean the ~ontainer wall of any material still ~3 2~ -..
. .

~ -` 1084468 clinging to it. The deflector 14 ensures complete discharge of tlle contento i~ a few ~econds.

- Although the embodiment shown in Fig. 2 is shown with the container 1 steeply inclined with respect to the horizontal, and since experiments have shown this to be preferable, the invention is of course not limited to this arrangement.

The hydraulic apparatus 22 shown diagrammatically in Fig. 1 so pivots the tool carrier 20 that the hi6h speed tool 4 is moved fully rightwards and outwards about the centre of gravity, from the upper position hown in solid lines into the low position shown in bro~en lines. By reason of the radial component, therefore, it beco~es ~ readily possible to move the high speed tool 4 toward6 and away from i ' ' ' the container centre 10.

It is important to note the opposite direction of rotation of the cbntainer 1 according to arrow 9 and of the high speed tools 4 according to arrow 13 in Fig. 1.

Fig. 2 shows the automatically opered and closed discharge orifice 12 disposed in the container bottom and which is shown in broken lines in the open position. Optionally, it is possible furthermore to provide a feed line 23 extending to deep down to the bottom of the container 1 and a suction pipe 24 at the top, on the container aperture. In the case of dry grinding non-bulky material, the machine ideally operates continuously. The fines are extracted from the streams ejected by the toothed discs in the direction of the arrow 25, through the suction pipe 24. Materials which are not suitable for vacuum extraction, particularly moist and wet materials, are discharged through the bottom orifice 12. In this case, the device for air supply and discharge 2~
..

--- ~084468 need not be provided. ~or need the air supply line be provided when bulky materials are bein~ processed. ~or this case, a large in-feed hopper 26 with a swingm g lid 27 i= idea.

Sho~n at the top of Fig. 4 is the hydraulic chucking'device 28, the pull rod 29 of which extends through the hollow shaft 5. In the example of embodiment shown in Fig. 4, this carries at the bottom a flange 30, 60 that'the toothed discs 3, 3", etc., with the associated spacer bushes 31 at the top, are easily accessible and can be locked ~' or released jointly for exchange purpoEes.

In Fig. 3, a toothed disc is shown which has three different segments of different tooth shape. The fine tooth shape 32 is unaffected particularly by large metallic foreign bodies, e.g. flat irons which may be present in refuse. ~owever, this shape does ~roduce rapid tearing-opén and pulverising of bags, cartons and similar large parts. In the processing of timber or similar materials without a hard material content, sharp teeth are used such as are shown for example at 3~ or 34. Toothed discs with radial'slots 33 are very slmple both to produce and maintain. Once the cutting edges which are used have been worn, it i sufficient to turn the toothed disc over and the cutting edges which we~e previously no ~ perating will engage the material.

In the case of the tooth form in group 34, the broken line 35 denotes that the actual impact face 36 (the cutting edge described above), is disposed radially in the lead when the direction of rotation is that indicated by the arrow 37.

~ igs. 5 to 8 show a similar but different embodiment of pulverising apparatus according to the invention, Fig. 5 showing the rotating container more steeply inclined, i.e. more intensely tilted with I ~ 2 7 i ,i .,~ .

. . ` ~ .

io~4468 respect to the horizontal. Furthermore, compared with the forms of embodiment shown in ~igs. 2 and 7, the ~iew in Fig. 5 lS indeed the same in principle but the inclination is a mirrored opposite. The .
form of embodiment sho~Jn in Figs. 5 to 8 is intended particularly for pre-pulverising, with a magnetic separation phase. The container 1 is therefore in this case driven at a below-critical speed and rotates in an anti-clockwise direction, as indicated by the arrow 9. The high ~ speed tool 4 according to Figs. 6 and 7 can be constructed in asimilar ; - manner as previously described in connection with Figs. 1 to 4.
~ ~ Another embodiment of the circular disc is to be described in greater i detail later with regard to another embodi~ent shown in Fies. 9 and 10.
The high speed tool 4 rotates indeed about its shaft 5 but, for the - rest, like the magnet 46, it is stationary, while the magnets 44 disposed on the walls of the container 1 ro~ate with the latter.
Figs. 5 and 6 show that here ~agnets 44 wh1ch are in each case .
1 staggered at 90 with respect to one another are, also as shown in .
Fig. 5, staggered in their height with respect to one another, over the total height of the container wall, and they may be either starting magnets or double magnets joined by a yoke, as mentioned at the outset. In either case, they are so fitted into the container walls, in non-magnetic plate, e.g. VA steel, that a relatively smooth transition is created on the inside. As the container 1 rotates, the material being treated, which is constantly turned over and-in motion, passes constantly through all four magnetic fields. As a~result, during the course of pre-pulverising, ferrous metal parts can very reliably be;picked up by a magnetic field, carried to a raised point above the discharge chute and let drop into it by the magnets being switched off. If plastic film, shreds of paper or textiles are held bet~Jeen iron parts and the rising magnet 44, they will be blo~m -: 28 -,. .
out through orifices 43 diFposed in the 6ides of the discharge chute 41 or will be blown out by the stream of air flowing through them, and thus will not pass into the discharge chute 41. ~he metal parts which on the other hand then lie ln the disch2rge chute 41 are passed out either by a vibrator 42, by an even ~teeper inclination than in the embodiment shown in Fig. 5, or in some other manner in the direction of the arrow shown in the discharge chute 41. It will be appreciated that the discharge chute 41 do~s not collide with the intake funnel 26, because it is expediently disposed at the side, as shown for example diagrammatically at the top in Fig. 6. This also shows the streams of air flowing out of the orifices 43 and carrying paper shreds. Reference 47 at the top in Fig. 6 denotes a scraper device for removing the metal part6 2 shown in the drawings and which are part of the material 2. Inst~ad of the scraper 47, it is possible also to provide a round brush or other suitable apparatus. These . . .
scraper means 47 can be omitted completely if it lS adequate for the ferrous metal parts picked up to be allowed to drop into the discharge chute 41 simply by the electromagnets being switched off.

Fi~. 6 shows at the bottom four diagrammatically indicated refuse bags which, after colliding with the toothed disc 3 which is rotating in the direction of the arrow 13, are cut open and then, in more dispersed form as indicated by the serpentine lines in Flg. 6, they drop by gravity into the bottom part of the container 1.

Fig. 5 shows on the right at the top the rim 45 of the container which is extended in non-ma~netic material and on the lower zone of which the fixedelongated curved magnet 46 is disposed. If, then, tin cans which emerge when the refuse bags are torn open, remaining on -top of the layer of material 2, attempt to roll do~mwards and over .

84g68 the edge, then they must do so through the field of the ~agnet 46, which holds them fast on the rim 45 and thus carries them upwards into the re~ion of the toothed disc tool shown on the left in Fig. 6.
Either they have already been picked up in the meantime by another revolving magnet 44 or they pass lower down into the layer of materials 2, so that in any event they'are prevented from rolling down the'surface again and cannot be passed over the rim'45 without be mg processed in some way.

If the apparatus shown in ~'igs. 7 and 8 is used as a fine pul-veriser, in which the container 1 is again caused to rotate at above-critical speed, then the discharge of dry pulverised material can either take place in the already-described manner, in the direction of the arrow 25, or, between the oothed discs 3 shown in Fig. 7 and the bearing of the toothed disc tool or beneath the V-belt pulley 6, a fan'55 is disposed, the impeller 56 is mounted on the shaft 5 of the toothed disc tool 4. The housing 57 of the fan 55 is ~ounted on the tool'carrier 20 of the V-belt drive 6, 7, 8 and the blo~m-out jet extends approximately at right-angles to the shaft 5, as can be seen from Fig. 8 and the position of the aperture of the fan 55 which'is shown therein. On the other hand, in the case of the embodiment shown in Fig. 7, there is on the intake aperture 58 of the fan 55 a throttling arrangement, not shown in greater detail, since throttling of the fann 55 expediently takes place on the intake side.

~ or the continuous working also of other than dry and powdered materials, it is possible to provide in the middle of the container bottom 53, on a connector 54 disposed rigidly thereon, a cover 50 which is not ri~idly connected to the connector 54 or the container bottom 53 but is driven by a Ceparate motor 52 at a separately controlled speed, being mounted on the shaft 51 thereof. Preferably, - ~ 30 ~this speed is so adjusted that the cover 50 rotates at a speed which iB slightly in advance of the connector 54 or the container bottom 53.
In Fig. 7, the Çaver piece 50 shown ïn a solid line i6 pressed on the connector 54, in order to keep the inlet aperture closed. On the other hand, in the broken-line position, the cover 50 - exaggeratedly drawn - is at a distance from the connector 54. For batch-wise operation, this distance is not exaggerated; instead, it is intended that as much material as possible should emerge quickly. With con-tinuous operation, on the other hand, the distance from the free edge - of the connector 54 to the more rapidly rotating cover 50 should be adjusted so that it is so small that just the desired quantity of material, comminuted to the desired degree of fineness, emerges continuously at the bottom.

. . . .
; According to the embodiment shown in Figs. 9 and 10, the toothed disc is differently constructed from that-shown in Fig. 3. It consists of a bottom carrier disc 60 having radially dispo6ed cut-outs 61 into which the teeth 32 which are plate-shaped, are inserted and secured by bolts 65. ~he bolts ensure attachment of the plate-like teeth 62 in a radial direction and the edges of the cut-outs 61 prevent tilting in a peripheral direction, even though a certain clearance, for example if the cut-outs are made or beaten out with substantial tolerances, ie not a disadvantage. After fitment of the teeth 62 into the cut-outs 61, a cover disc 63 is placed on top and secured , . . .
; by means of screws. The ring of screws disposed above the periphery can be clearly seen in Fig. 10, although lt is not identified by a reference numeral. The armouring of the plates is indicated at 64.

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3 1

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A pulverising apparatus comprising a rotatably driven container and at least one eccentrically disposed rotatably driven high-speed tool having a shaft disposed approximately parallel with the axis of the container, char-acterised in that the high-speed tool is provided with at least one toothed disc, the plane of which is transverse to the tool shaft and which partially dips into material to be pulverised which is present at the container wall, and in that the high-speed tool is generally radially displaceable in the container.

2. Apparatus according to claim 1, characterised in that for the pur-poses of fine pulverising, the container is driven at above-critical speed, and in that the direction of rotation of the high-speed tool is opposite to that of the adjacent container wall.

3. Apparatus according to claim 1, characterised in that the high speed tool comprises a plurality of toothed discs so disposed one above another and at a distance from one another on the shaft that material pressed against the container wall remains there in a roll at the height of the intermediate space.

4. Apparatus according to claim 1, 2 or 3, characterised in that the tool shaft is displaceable in an axial direction.

5. Apparatus according to claim 1, 2 or 3, characterised in that a plurality of high-speed tools are eccentrically disposed in the container.

6. Apparatus according to claim 3, characterised in that for pre-pulver-ising, the container is driven at a below-critical speed.

7. Apparatus according to claim 1, characterised in that the axis of the container is inclined with respect to the horizontal.

8. Apparatus according to claim 6, characterised in that at least one magnet is rigidly mounted on the container, said magnet having a working side, facing the interior of the container, disposed in the regularly curved face of the container wall, and in that a discharge chute is provided in the con-tainer.

9. Apparatus according to claim 8, characterised in that at least two magnets which can be switched off are regularly distributed over the container wall.

10. Apparatus according to claim 9, characterised in that there are four magnets.

11. Apparatus according to claim 9 or 10, characterised in that the magnets are distributed peripherally over the container wall.

12. Apparatus according to claim 9 or 10, characterised in that the magnets are distributed over the height of the container wall.

13. Apparatus according to claim 9 or 10, characterised in that the magnets are distributed both peripherally and axially over the container wall.

14. Apparatus according to claim 8, characterised in that above the dis-charge chute and next to the inside wall of the container there is a scraper device.

15. Apparatus according to claim 14, characterised in that the scraper device is a round brush.

16. Apparatus according to claim 14, characterised in that alongside the discharge chute there is a fan and blow-out orifices to generate a stream of air which blows over the discharge area.

17. Apparatus according to claim 1, 2 or 3, characterised in that a discharge orifice which can be closed by a cover is provided in the container bottom.

18. Apparatus according to claim 17, characterised in that for continu-ous operation, the cover is mounted on the shaft of a separate motor and is preferably driven at a speed which is in advance of the container bottom.

19. Apparatus according to claim 18, characterised in that the cover is disposed on a connector mounted on the outside of the container bottom, at least one curved discharge fin of low height being attached to the cover.

20. Apparatus according to claim 1, 2 or 3, characterised in that for continuous operation with dry materials, a suction pipe, a feed line and a cover are provided on the upper container aperture.

21. Apparatus according to claim 1, 2 or 3, characterised in that be-tween the toothed disc or discs and the bearing for the shaft which carries the toothed disc, there is a fan, the impeller of which is mounted on the shaft, the housing of which is mounted on a tool carrier of a V-belt drive and a blow-out jet which extends more or less at right-angles to the tool shaft, and in that a throttling arrangement is provided on an intake aperture of the fan.

22. Apparatus according to claim 1, characterised in that the toothed disc has a thickness of 2 to 12 mm and a diameter of 100 to 900 mm.

23. Apparatus according to claim 1, characterised in that the toothed disc has a thickness of 2.5 to 8 mm, and a diameter of 300 to 750 mm.

24. Apparatus according to claim 22 or 23, characterised in that impact faces of the teeth are disposed radially of the toothed disc.

25. Apparatus according to claim 22 or 23, characterised in that impact faces of the teeth slope outwardly of the disc in the direction of rotation thereof.

26. Apparatus according to claim 1, characterised in that the toothed disc has a bottom carrier disc with radially disposed cut-outs, teeth which are adapted to be inserted into the cut-outs and mounted on the carrier disc, and a cover disc to fit on top.

27. Apparatus according to claim 26, characterised in that the teeth consist of rectangular flat plates.

28. Apparatus according to claim 26, characterised in that the teeth are armoured in places.

29. Apparatus according to claim 1, 2 or 3, characterised in that an outer free rim of the container consists of non-magnetic material over the whole periphery and in that, in a lower zone of the container there is a fixed elongated magnet.